Method of processing substrate, method of manufacturing semiconductor device, recording medium, and substrate processing apparatus

ABSTRACT

There is provided a technique that includes: etching a first film exposed on a surface of a substrate by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing: (a) forming a first modified layer in at least a portion of a surface of the first film by supplying a first gas to the substrate; and (b) etching at least a portion of the first film with an etching species, the etching species being generated by supplying a second gas having a molecular structure different from that of the first gas to the substrate to perform at least one selected from the group of causing the second gas to react with the first modified layer and activating the first modified layer with the second gas.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority from U.S. patent application Ser. No. 17/377,990, filed Jul. 16, 2021, and Japanese Patent Application No. 2020-122454, filed on Jul. 16, 2020, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a method of manufacturing a semiconductor device, a method of processing a substrate, a substrate processing apparatus, and a recording medium.

BACKGROUND

In the related art, as a process of manufacturing a semiconductor device, a process of etching a film exposed on a surface of a substrate may be carried out.

With scaling of semiconductor devices, processing dimensions are becoming finer and more complicated, and as a result, a high-precision patterning process including the above-mentioned etching process is performed many times, which causes an increase in cost. On the other hand, there is a technique of performing the above-mentioned etching process at an atomic layer level (which is hereinafter also referred to as atomic layer etching), and such a process having high controllability has attracted attention as a useful technique in reducing the number of steps. In the related art, the technique related to the atomic layer etching has mainly been a method using plasma.

In the related-art etching of a film with an etching gas, an etching amount depends on a partial pressure (supply amount) of the etching gas. Therefore, a pressure distribution of the gas in a reaction system causes a difference in the etching amount. For example, when etching a film formed inside a groove, even with the same process time, a film formed at the bottom of a deep groove where a gas is difficult to be supplied has an etching amount smaller than that of a film formed near an opening of the groove where the gas is easily supplied. In this manner, in the related-art etching process of the film with the etching gas, there is a need to improve a controllability of the etching amount.

SUMMARY

Some embodiments of the present disclosure provide a technique capable of enhancing a controllability of an etching amount.

According to embodiments of the present disclosure, there is provided a technique that includes: etching a first film exposed on a surface of a substrate by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing: (a) forming a first modified layer in at least a portion of a surface of the first film by supplying a first gas to the substrate; and (b) etching at least a portion of the first film with an etching species, the etching species being generated by supplying a second gas having a molecular structure different from that of the first gas to the substrate to perform at least one selected from the group of causing the second gas to react with the first modified layer and activating the first modified layer with the second gas.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic configuration view of a vertical process furnace 202 of a substrate processing apparatus suitably used in embodiments of the present disclosure, in which a portion of the process furnace 202 is shown in a vertical cross section.

FIG. 2 is a schematic configuration view of a vertical process furnace 202 of a substrate processing apparatus suitably used in embodiments of the present disclosure, in which a portion of the process furnace 202 is shown in a cross section taken along a line A-A in FIG. 1 .

FIG. 3 is a schematic configuration diagram of a controller 121 of a substrate processing apparatus suitably used in embodiments of the present disclosure, in which a control system of a controller 121 is shown in a block diagram.

FIG. 4 is a diagram showing a gas supply sequence of etching process in embodiments of the present disclosure.

FIG. 5A is a partially-enlarged cross-sectional view of a wafer 200 with a base 200 a exposed on a surface of the wafer 200 in a state where a first gas 10 is supplied to the wafer 200 and is adsorbed on the surface of the base 200 a to form a first modified layer 200 b. FIG. 5B is a partially-enlarged cross-sectional view of the wafer 200 in a state where a second gas 20 is supplied to the wafer 200 on which the first modified layer 200 b is formed. FIG. 5C is a partially-enlarged cross-sectional view of the wafer 200 in a state where the first modified layer 200 b is activated by the second gas 20 and an etching species 200 c is generated. FIG. 5D is a partially-enlarged cross-sectional view of the wafer 200 in a state where a portion of the surface of the base 200 a is etched by the etching species 200 c to generate a first product 12 and a second product 14 at the time of etching. FIG. 5E is a partially-enlarged cross-sectional view of the wafer 200 showing behaviors of the first product 12 and the second product 14 on the surface of the base 200 a whose surface is partially etched. FIG. 5F is a partially-enlarged cross-sectional view of the wafer 200 in a state where the second product 14 remains and/or is adsorbed on the surface of the base 200 a whose surface is partially etched. FIG. 5G is a partially-enlarged cross-sectional view of the wafer 200 in a state where at least one selected from the group of the second product 14, the second gas 20, and the base 200 a whose surface is partially etched reacts to form a second modified layer 200 d on the surface of the base 200 a whose surface is partially etched. FIG. 5H is a partially-enlarged cross-sectional view of the wafer 200 in a state where the first gas 10 is supplied to the wafer 200 in which the second modified layer 200 d is formed on the surface of the base 200 a whose surface is partially etched and the first gas is adsorbed on the surface of the second modified layer 200 d. FIG. 5I is a partially-enlarged cross-sectional portion of the wafer 200 in a state where the first gas 10 reacts with the second modified layer 200 d to generate a product 30 on the surface of the base 200 a whose surface is partially etched. FIG. 5J is a partially-enlarged cross-sectional view of the wafer 200 in a state where the product 30 generated on the surface of the base 200 a whose surface is partially etched is desorbed from the surface of the base 200 a. FIG. 5K is a partially-enlarged cross-sectional view of the wafer 200 in a state where the surface of the base 200 a whose surface is partially etched is exposed again after the product 30 on the surface of the base 200 a whose surface is partially etched is desorbed.

FIG. 6 is a diagram showing a measurement result of an etching rate in a first comparative example.

FIG. 7 is a diagram showing the measurement result of an etching rate in a second comparative example.

FIG. 8 is a diagram showing a measurement result of an etching rate in embodiments of the present disclosure.

FIG. 9A is a partially-enlarged cross-sectional view of a wafer 200 with a base 200 a and a base 200 e exposed on the surface of the wafer 200 in a state before an etching process is performed on the wafer 200. FIG. 9B is a partially-enlarged cross-sectional view of the wafer 200 in a state during etching process when the etching process is performed on the wafer 200 with the base 200 a and the base 200 e exposed on the surface of the wafer 200. FIG. 9C is a partially-enlarged cross-sectional view of the wafer 200 in a state after the etching process is performed on the wafer 200 with the base 200 a and the base 200 e exposed on the surface of the wafer 200.

DETAILED DESCRIPTION Embodiments of the Present Disclosure

Embodiments of the present disclosure will be now described with reference to FIGS. 1 to 4 and FIGS. 5A to 5K. The drawings used in the following description are schematic, and dimensional relationships, ratios, and the like of various elements on the drawings may not match actual ones. Further, the dimensional relationship, ratios, and the like of various elements between plural drawings may not match each other.

(1) Configuration of Substrate Processing Apparatus

As illustrated in FIG. 1 , a process furnace 202 includes a heater 207 as a heating mechanism (a temperature regulator or a temperature regulation part). The heater 207 has a cylindrical shape and is supported by a holding plate to be vertically installed. The heater 207 functions as an activation mechanism (an excitation part) configured to thermally activate (excite) a gas.

A reaction tube 203 is disposed inside the heater 207 to be concentric with the heater 207. The reaction tube 203 is made of a heat resistant material, e.g., quartz (SiO₂), silicon carbide (SiC) or the like, and has a cylindrical shape with its upper end closed and its lower end opened. A manifold 209 is disposed below the reaction tube 203 in a concentric relationship with the reaction tube 203. The manifold 209 is made of a metal material such as, e.g., stainless steel (SUS), and has a cylindrical shape with its upper and lower ends opened. The upper end of the manifold 209 engages with the lower end of the reaction tube 203. The manifold 209 is configured to support the reaction tube 203. An O-ring 220 a as a seal member is installed between the manifold 209 and the reaction tube 203. Similar to the heater 207, the reaction tube 203 is vertically installed. A processing vessel (reaction vessel) mainly includes the reaction tube 203 and the manifold 209. A process chamber 201 is formed in a hollow cylindrical portion of the processing vessel. The process chamber 201 is configured to be capable of accommodating wafers 200 as substrates. The processing of the wafers 200 is performed in the process chamber 201.

Nozzles 249 a to 249 c as first to third supply parts are installed in the process chamber 201 to penetrate a sidewall of the manifold 209. The nozzles 249 a to 249 c will also be referred to as first to third nozzles, respectively. The nozzles 249 a to 249 c are each made of a heat resistant material such as quartz or SiC. Gas supply pipes 232 a to 232 c are respectively connected to the nozzles 249 a to 249 c. The nozzles 249 a to 249 c are different nozzles, in which each of the nozzles 249 a and 249 c is installed adjacent to the nozzle 249 b.

Mass flow controllers (MFCs) 241 a to 241 c, which are flow rate controllers (flow rate control parts), and valves 243 a to 243 c, which are opening/closing valves, are installed in the gas supply pipes 232 a to 232 c sequentially from corresponding upstream sides of gas flow respectively. Gas supply pipes 232 d to 232 f are connected to the gas supply pipes 232 a to 232 c at the downstream side of the valves 243 a to 243 c, respectively. MFCs 241 d to 241 f and valves 243 d to 243 f are installed at the gas supply pipes 232 d to 232 f sequentially from corresponding upstream sides of gas flow respectively. The gas supply pipes 232 a to 232 f are made of, for example, a metal material such as stainless steel (SUS).

As illustrated in FIG. 2 , the nozzles 249 a to 249 c are disposed in a space with an annular plan-view shape between the inner wall of the reaction tube 203 and the wafers 200 such that the nozzles 249 a to 249 c extend upward along an arrangement direction of the wafers 200 from a lower portion to an upper portion of the inner wall of the reaction tube 203. Specifically, the nozzles 249 a to 249 c are respectively installed at a lateral side of a wafer arrangement region in which the wafers 200 are arranged, namely in a region which horizontally surrounds the wafer arrangement region, to extend along the wafer arrangement region. The nozzle 249 b is disposed to face an exhaust port 231 a to be described below, on a straight line in a plane view, with centers of the wafers 200 loaded into the process chamber 201 interposed therebetween. The nozzles 249 a and 249 c are disposed to sandwich a straight line L passing through the nozzle 249 b and a center of the exhaust port 231 a from both sides along the inner wall of the reaction tube 203 (an outer peripheral portion of the wafers 200). The straight line L is also a straight line passing through the nozzle 249 b and the centers of the wafers 200. That is, it may be said that the nozzle 249 c is installed at the opposite side of the nozzle 249 a with the straight line L interposed therebetween. The nozzles 249 a and 249 c are disposed in line symmetry with the straight line L as a symmetry axis. Gas supply holes 250 a to 250 c configured to supply a gas are installed on the side surfaces of the nozzles 249 a to 249 c, respectively. The gas supply holes 250 a to 250 c are respectively opened to face the exhaust port 231 a in the plane view, thus allowing a gas to be supplied toward the wafers 200. The gas supply holes 250 a to 250 c may be formed in a plural number between the lower portion and the upper portion of the reaction tube 203.

A first gas is supplied from the gas supply pipe 232 a into the process chamber 201 via the MFC 241 a, the valve 243 a, and the nozzle 249 a. The first gas acts as a modifier or a modifying gas.

A second gas is supplied from the gas supply pipe 232 b into the process chamber 201 via the MFC 241 b, the valve 243 b, and the nozzle 249 b. The second gas is a gas having a molecular structure different from that of the first gas. The second gas acts as an activation gas or a reaction gas.

A third gas is supplied from the gas supply pipe 232 c into the process chamber 201 via the MFC 241 c, the valve 243 c, and the nozzle 249 c. The third gas acts as a preprocessing gas.

An inert gas is supplied from the gas supply pipes 232 d to 232 f into the process chamber 201 via the MFCs 241 d to 241 f, the valves 243 d to 243 f, the gas supply pipes 232 a to 232 c, and the nozzles 249 a to 249 c, respectively. The inert gas acts as a purge gas, a carrier gas, a dilution gas, or the like.

A first gas supply system (a modifier supply system or a modifying gas supply system) mainly includes the gas supply pipe 232 a, the MFC 241 a, and the valve 243 a. A second gas supply system (an activation gas supply system or a reaction gas supply system) mainly includes the gas supply pipe 232 b, the MFC 241 b, and the valve 243 b. A third gas supply system (a preprocessing gas supply system) mainly includes the gas supply pipe 232 c, the MFC 241 c, and the valve 243 c. An inert gas supply system mainly includes the gas supply pipes 232 d to 232 f, the MFCs 241 d to 241 f, and the valves 243 d to 243 f.

One or all of the aforementioned various gas supply systems may be configured as an integrated gas supply system 248 in which the valves 243 a to 243 f, the MFCs 241 a to 241 f and the like are integrated. The integrated gas supply system 248 is connected to each of the gas supply pipes 232 a to 232 f. In addition, the integrated gas supply system 248 is configured such that operations of supplying various gases into the gas supply pipes 232 a to 232 f (that is, opening/closing operations of the valves 243 a to 243 f, flow rate regulation operations by the MFCs 241 a to 241 f, and the like) are controlled by a controller 121 to be described below. The integrated gas supply system 248 is configured as an integral type or division type integrated unit, and may be attached to and detached from the gas supply pipes 232 a to 232 f and the like on an integrated unit basis, such that maintenance, replacement, extension, and the like of the integrated gas supply system 248 may be performed on the integrated unit basis.

The exhaust port 231 a configured to exhaust an internal atmosphere of the process chamber 201 is installed at a lower side of the sidewall of the reaction tube 203. As illustrated in FIG. 2 , the exhaust port 231 a is installed at a position facing the nozzles 249 a to 249 c (the gas supply holes 250 a to 250 c) in the plane view, with the wafers 200 interposed therebetween. The exhaust port 231 a may be installed between the lower portion and the upper portion of the sidewall of the reaction tube 203, that is, along the wafer arrangement region. An exhaust pipe 231 is connected to the exhaust port 231 a.

A vacuum pump 246 as a vacuum exhaust device is connected to the exhaust pipe 231 via a pressure sensor 245 as a pressure detector (pressure detection part) configured to detect an internal pressure of the process chamber 201 and an auto pressure controller (APC) valve 244 as a pressure regulator (pressure regulation part). The APC valve 244 is configured such that a vacuum exhaust and a vacuum exhaust stop of the interior of the process chamber 201 can be performed by opening and closing the APC valve 244 while operating the vacuum pump 246 and such that the internal pressure of the process chamber 201 can be regulated by adjusting an opening degree of the APC valve 244 based on pressure information detected by the pressure sensor 245 while operating the vacuum pump 246. An exhaust system mainly includes the exhaust pipe 231, the APC valve 244, and the pressure sensor 245. The vacuum pump 246 may be included in the exhaust system.

A seal cap 219, which serves as a furnace opening lid configured to be capable of hermetically sealing a lower end opening of the manifold 209, is installed under the manifold 209. The seal cap 219 is made of a metal material such as stainless steel (SUS), and is formed in a disc shape. An O-ring 220 b, which is a seal member making contact with the lower end portion of the manifold 209, is installed on an upper surface of the seal cap 219.

A rotation mechanism 267 configured to rotate a boat 217 to be described below is installed under the seal cap 219. A rotary shaft 255 of the rotation mechanism 267, which penetrates the seal cap 219, is connected to the boat 217. The rotation mechanism 267 is configured to rotate the wafers 200 by rotating the boat 217. The seal cap 219 is configured to be vertically moved up or down by a boat elevator 115 which is an elevator mechanism installed outside the reaction tube 203. The boat elevator 115 is configured as a transfer device (transfer mechanism) which loads and unloads (transfers) the wafers 200 into and from (out of) the process chamber 201 by moving the seal cap 219 up or down.

A shutter 219 s as a furnace opening lid capable of hermetically sealing the lower end opening of the manifold 209, with the boat 217 unloaded from the interior of the process chamber 201 by moving the seal cap 219 down, is installed under the manifold 209. The shutter 219 s is made of a metal material such as stainless steel (SUS), and is formed in a disc shape. An O-ring 220 c as a seal member making contact with the lower end portion of the manifold 209 is installed on an upper surface of the shutter 219 s. An opening/closing operation (an up-down movement operation, a rotational movement operation, and the like) of the shutter 219 s is controlled by a shutter opening/closing mechanism 115 s.

The boat 217 serving as a substrate support is configured to support a plurality of wafers 200, for example, 25 to 200 wafers, in such a state that the wafers 200 are arranged in a horizontal posture and in multiple stages along a vertical direction with the centers of the wafers 200 aligned with one another. That is, the boat 217 is configured to arrange the wafers 200 in a spaced-apart relationship. The boat 217 is made of a heat resistant material such as quartz or SiC. Heat insulating plates 218 made of a heat resistant material such as quartz or SiC are installed below the boat 217 in multiple stages.

A temperature sensor 263 serving as a temperature detector is installed in the reaction tube 203. Based on temperature information detected by the temperature sensor 263, a state of supplying electric power to the heater 207 is regulated such that the interior of the process chamber 201 has a desired temperature distribution. The temperature sensor 263 is installed along the inner wall of the reaction tube 203.

As illustrated in FIG. 3 , the controller 121, which is a control part (control means), may be configured as a computer including a central processing unit (CPU) 121 a, a random access memory (RAM) 121 b, a memory device 121 c, and an I/O port 121 d. The RAM 121 b, the memory device 121 c and the I/O port 121 d are configured to be capable of exchanging data with the CPU 121 a via an internal bus 121 e. An input/output device 122 configured as, for example, a touch panel or the like, is connected to the controller 121.

The memory device 121 c includes, for example, a flash memory, a hard disk drive (HDD), a solid state drive (SSD), or the like. A control program that controls operations of a substrate processing apparatus, a process recipe in which sequences, conditions, and the like of substrate processing to be described below are described, and the like are readably stored in the memory device 121 c. The process recipe functions as a program configured to be capable of causing the controller 121 to execute each sequence in the substrate processing to be described below, to obtain a predetermined result. Hereinafter, the process recipe and the control program will be generally and simply referred to as a “program.” Furthermore, the process recipe will be simply referred to as a “recipe.” When the term “program” is used herein, it may indicate a case of including only the recipe, a case of including only the control program, or a case of including both the recipe and the control program. The RAM 121 b is configured as a memory area (work area) in which a program, data and the like read by the CPU 121 a are temporarily stored.

The I/O port 121 d is connected to the MFCs 241 a to 241 f, the valves 243 a to 243 f, the pressure sensor 245, the APC valve 244, the vacuum pump 246, the temperature sensor 263, the heater 207, the rotation mechanism 267, the boat elevator 115, the shutter opening/closing mechanism 115 s, and the like.

The CPU 121 a is configured to read the control program from the memory device 121 c and execute the same. The CPU 121 a also reads the recipe from the memory device 121 c according to an input of an operation command from the input/output device 122. In addition, the CPU 121 a is configured to control, according to the contents of the recipe thus read, the flow rate regulating operation of various types of gases by the MFCs 241 a to 241 f, the opening/closing operation of the valves 243 a to 243 f, the opening/closing operation of the APC valve 244, the pressure regulating operation performed by the APC valve 244 based on the pressure sensor 245, the driving and stopping of the vacuum pump 246, the temperature regulating operation performed by the heater 207 based on the temperature sensor 263, the operation of rotating the boat 217 and adjusting the rotation speed of the boat 217 with the rotation mechanism 267, the operation of moving the boat 217 up or down with the boat elevator 115, the operation of opening and closing the shutter 219 s with the shutter opening/closing mechanism 115 s, and the like.

The controller 121 may be configured by installing, on the computer, the aforementioned program stored in an external memory device 123. The external memory device 123 may include, for example, a magnetic disc such as a HDD, an optical disc such as a CD, a magneto-optical disc such as a MO, a semiconductor memory such as a USB memory and a SSD, and the like. The memory device 121 c or the external memory device 123 is configured as a computer-readable recording medium. Hereinafter, the memory device 121 c and the external memory device 123 will be generally and simply referred to as a “recording medium.” When the term “recording medium” is used herein, it may indicate a case of including only the memory device 121 c, a case of including only the external memory device 123, or a case of including both the memory device 121 c and the external memory device 123. Furthermore, the program may be supplied to the computer by using a communication means such as the Internet or a dedicated line, instead of using the external memory device 123.

(2) Substrate Processing Process

As a process of manufacturing a semiconductor device process using the above-described substrate processing apparatus, an etching process sequence example of etching a base 200 a as a first film exposed on the surface of a wafer 200 as a substrate, that is, a gas supply sequence example in an etching process, will be described with reference to FIG. 4 and FIGS. 5A to 5K. In the following descriptions, operations of the respective parts constituting the substrate processing apparatus are controlled by the controller 121.

A gas supply sequence shown in FIG. 4 , includes etching a base 200 a, which is a first film exposed on the surface of a wafer 200, by performing a cycle a predetermined number of times (n times, where n is an integer of 1 or more), the cycle including non-simultaneously performing:

step A of forming a first modified layer 200 b in at least a portion of the base 200 a by supplying a first gas to the wafer 200; and

step B of etching at least a portion of the base 200 a with an etching species, the etching species being generated by supplying a second gas having a molecular structure different from that of the first gas to the wafer 200 to perform at least one selected from the group of causing the second gas to react with the first modified layer 200 b and activating the first modified layer 200 b with the second gas.

In the gas supply sequence shown in FIG. 4 , each step (that is, step A and step B) is performed in a non-plasma atmosphere.

In the present disclosure, for the sake of convenience, the above-described process sequence may be denoted as follows. The same denotation may be used in modifications and the like to be described below.

(First gas→Second gas)×n

When the term “wafer” is used in the present disclosure, it may refer to “a wafer itself” or “a wafer and a laminated body of certain layers or films formed on a surface of the wafer.” When the phrase “a surface of a wafer” is used in the present disclosure, it may refer to “a surface of a wafer itself” or “a surface of a certain layer formed on a wafer.” When the expression “a certain layer is formed on a wafer” is used in the present disclosure, it may mean that “a certain layer is formed directly on a surface of a wafer itself” or that “a certain layer is formed on a layer formed on a wafer.” When the term “substrate” is used in the present disclosure, it may be synonymous with the term “wafer.”

Further, when the term “base” is used in the present disclosure, it may refer to “a wafer itself” or “a certain layer or film formed on a surface of the wafer.” When the phrase “a surface of a base” is used in the present disclosure, it may refer to “a surface of a wafer itself” or “a surface of a certain layer formed on a surface of a wafer.” When the expression “a certain layer is formed on a surface of a base” is used in the present disclosure, it may mean that “a certain layer is formed directly on a surface of a wafer itself” or that “a certain layer is formed on a surface of a layer formed on a surface of a wafer.”

Wafer Charging and Boat Loading

When the boat 217 is charged with a plurality of wafers 200 (wafer charging), the shutter 219 s is moved by the shutter opening/closing mechanism 115 s to open the lower end opening of the manifold 209 (shutter opening). Thereafter, as shown in FIG. 1 , the boat 217 supporting the wafers 200 is lifted up by the boat elevator 115 and is loaded into the process chamber 201 (boat loading). In this state, the seal cap 219 seals the lower end of the manifold 209 via the O-ring 220 b. In addition, the base 200 a as the first film, which is a target of the etching process, is exposed on the surface of the wafer 200. The base 200 a includes, for example, a silicon-based nitrogen-containing film such as a silicon nitride film (SiN film).

Pressure Regulation and Temperature Regulation

The interior of the process chamber 201, that is, a space where the wafers 200 are placed, is vacuum-evacuated (decompression-evacuated) by the vacuum pump 246 to reach a desired pressure (vacuum degree). In this operation, the internal pressure of the process chamber 201 is measured by the pressure sensor 245, and the APC valve 244 is feedback-controlled based on the measured pressure information. Further, the wafers 200 in the process chamber 201 are heated by the heater 207 to have a desired processing temperature. In this operation, a state of supplying electric power to the heater 207 is feedback-controlled based on the temperature information detected by the temperature sensor 263 such that the interior of the process chamber 201 has a desired temperature distribution. Further, rotation of the wafers 200 by the rotation mechanism 267 begins. The evacuation of the interior of the process chamber 201, and the heating and rotation of the wafers 200 are continuously performed at least until the processing on the wafers 200 is completed.

Etching Process

Then, a first cycle non-simultaneously performing the steps A and B described below is executed a predetermined number of times.

Step A

In step A, a first gas is supplied to the wafer 200, that is, to the wafer 200 with the base 200 a as the first film exposed on the surface of the wafer 200 in the process chamber 201.

Specifically, the valve 243 a is opened to allow the first gas to flow into the gas supply pipe 232 a. A flow rate of the first gas is regulated by the MFC 241 a. The first gas is supplied into the process chamber 201 via the nozzle 249 a, flows over the surface of the wafer 200, and is exhausted via the exhaust port 231 a. In this operation, the first gas is supplied to the wafer 200. Further, at this time, the valves 243 d to 243 f may be opened to allow an inert gas to be supplied into the process chamber 201 via the nozzles 249 a to 249 c, respectively.

By supplying the first gas to the wafer 200 under conditions to be described below, it is possible to modify the surface of the base 200 a uniformly. Specifically, as shown in FIG. 5A, when the first gas 10 is supplied to the wafer 200 with the base 200 a exposed on the surface of the wafer 200, the first gas 10 is uniformly adsorbed in the surface of the base 200 a to form a first modified layer 200 b.

The first modified layer 200 b is formed by at least one selected from the group of causing at least a portion of molecules of the first gas 10 to be physically or chemically adsorbed on at least a portion of the surface of the base 200 a (hereinafter, also referred to as modification by adsorption) and generating a compound by a chemical reaction between at least a portion of the molecules of the first gas 10 and at least a portion of atoms or molecules on the surface of the base 200 a (hereinafter, also referred to as modification by compound generation). That is, in this step, it is possible to modify the surface of the base 200 a by the modification by adsorption and/or the modification by compound generation by using the first gas 10. FIG. 5A shows, as an example, the first modified layer 200 b formed by causing at least a portion of the molecules of the first gas 10 to be adsorbed on at least a portion of the surface of the base 200 a.

In the modification by adsorption, a modified portion (that is, a portion where the first modified layer 200 b is formed) of the base 200 a serves as a base of an etching species to be generated in step B to be described below. Therefore, an amount of etching species to be generated in step B may be controlled by an amount of adsorption of the first gas on the surface of the base 200 a. Similarly, in the modification by compound generation, a modified portion (that is, a portion where the first modified layer 200 b is formed) of the base 200 a serves as a base of the etching species to be generated in step B to be described below. Therefore, the amount of etching species to be generated in step B may be controlled by the amount of compound generated on the surface of the base 200 a. Then, under conditions to be described below, the first modified layer 200 b can be uniformly formed in the surface of the base 200 a, whereby in step B to be described below, it is possible to uniformly generate the etching species in the surface of the base 200 a.

Depending on process conditions, a self-limit may be generated in the reaction by which the first modified layer 200 b is formed. That is, depending on the process conditions, a modification reaction by adsorption may be saturated, and a modification reaction by compound generation may also be saturated. By saturating the reaction by which the first modified layer 200 b is formed, it is possible to form the first modified layer 200 b more uniformly in the surface of the base 200 a. As a result, in step B to be described below, it is possible to generate the etching species more uniformly in the surface of the base 200 a.

After the formation of the first modified layer 200 b on the surface of the base 200 a is completed, the valve 243 a is closed to stop the supply of the first gas into the process chamber 201. Then, the interior of the process chamber 201 is vacuum-evacuated to remove a gas and the like remaining in the process chamber 201 from the interior of the process chamber 201. At this time, the valves 243 d to 243 f may be opened to allow an inert gas to be supplied into the process chamber 201 via the nozzles 249 a to 249 c. The inert gas supplied from the nozzles 249 a to 249 c acts as a purge gas, whereby the interior of the process chamber 201 is purged (purge). The purge with the inert gas may not be performed. The purge removes the first gas 10 and the like that are not adsorbed on the wafer 200 while leaving the first modified layer 200 b on the surface of the base 200 a.

A process condition when the first gas is supplied in step A is exemplified as follows:

Processing temperature: 25 to 400 degrees C., specifically 50 to 250 degrees C.

Processing pressure: 1 to 13,300 Pa, specifically 50 to 2,660 Pa

First gas supply flow rate: 1 to 5,000 sccm, specifically 50 to 2,000 sccm

First gas supply time: 1 to 3,000 seconds, specifically 10 to 1,200 seconds

Inert gas supply flow rate (for each gas supply pipe): 100 to 5,000 sccm, specifically 100 to 3,000 sccm

In the present disclosure, a notation of a numerical range such as “25 to 400 degrees C.” means that a lower limit value and an upper limit value are included in the range. For example, “25 to 400 degrees C.” means “25 degrees C. or higher and 400 degrees C. or lower.” The same applies to other numerical ranges. Further, the processing temperature means a temperature of the wafer 200, and the processing pressure means an internal pressure of the process chamber 201. The same applies to the following description.

In the aforementioned process condition, by setting the processing temperature to 25 degrees C. or higher, specifically 50 degrees C. or higher, it is possible to form the first modified layer 200 b at a practical formation rate. Further, in the aforementioned process condition, by setting the processing temperature to 400 degrees C. or lower, specifically 250 degrees C. or lower, it is possible to form the first modified layer 200 b in the surface of the base 200 a while suppressing the first film (base 200 a) being directly etched by the first gas.

In this step, the first gas may be supplied to the wafer 200 under a condition that the reaction by which the first modified layer 200 b is formed may be saturated. Thus, it possible to form the first modified layer 200 b more uniformly in the surface of the base 200 a. For example, by setting the processing temperature to a predetermined temperature of 250 degrees C. or lower, specifically 200 degrees C. or lower, more specifically 150 degrees C. or lower, it is possible to saturate the reaction by which the first modified layer 200 b is formed. Even when the processing temperature is set to such a temperature, the reaction by which the first modified layer 200 b is formed may be unsaturated by regulating conditions other than the processing temperature (for example, shortening the first gas supply time, lowering the processing pressure, and the like).

Further, the aforementioned process conditions may be conditions that when the first gas is present alone (that is, when the first gas is supplied alone to the wafer 200 having the exposed base 200 a, the same applies hereinafter.), it is difficult to continue the etching reaction of the base 200 a. Further, the aforementioned process conditions may be conditions that when the second gas is present alone (that is, when the second gas is supplied alone to the wafer 200 having the exposed base 200 a, the same applies hereinafter.), it is difficult to continue the etching reaction of the base 200 a.

A process condition when the purging with the inert gas is performed in step A is exemplified as follows:

Processing temperature: 25 to 400 degrees C., specifically 50 to 250 degrees C.

Processing pressure: 1 to 13,300 Pa, specifically 50 to 1,330 Pa

Inert gas supply flow rate (for each gas supply pipe): 100 to 5,000 sccm, specifically 500 to 3,000 sccm

Inert gas supply time: 1 to 600 seconds, specifically 10 to 120 seconds

The first gas used in step A is not particularly limited as long as it is a gas capable of modifying the surface of the base 200 a which is the first film.

Examples of the first gas may include a silicon (Si)-containing gas, a metal-containing gas, an oxygen (O)-containing gas, a nitrogen (N)- and hydrogen (H)-containing gas, a boron (B)-containing gas, a phosphorus (P)-containing gas, a halogen-containing gas, and the like. One or more of these gases may be used as the first gas.

An example of the Si-containing gas exemplified as an example of the first gas may include an aminosilane-based gas which is a gas containing Si and an amino group.

Here, the amino group refers to a functional group obtained by coordinating one or two hydrocarbon groups containing one or more carbon (C) atoms to one nitrogen (N) atom (a functional group obtained by substituting one or both of H's of an amino group represented by NH₂ with a hydrocarbon group containing one or more C atoms). When two hydrocarbon groups constituting a portion of the amino group are coordinated to one N, the two hydrocarbon groups may be the same hydrocarbon group or different hydrocarbon groups. The hydrocarbon group may contain a single bond like an alkyl group or may contain an unsaturated bond such as a double bond or a triple bond. The amino group may have a cyclic structure. Since the amino group is bonded to Si, which is the central atom of the aminosilane molecule, the amino group in aminosilane may be referred to as a ligand or an amino ligand. The aminosilane-based gas may contain Si and an amino group and may further contain a hydrocarbon group. The hydrocarbon group may contain a single bond like an alkyl group or may contain an unsaturated bond such as a double bond or a triple bond. The hydrocarbon group may have a cyclic structure. The hydrocarbon group may be bonded to Si which is the central atom of the aminosilane molecule. In this case, the hydrocarbon group in aminosilane may also be referred to as a ligand or a hydrocarbon ligand. When the hydrocarbon group is an alkyl group, this hydrocarbon group may also be referred to as an alkyl ligand. Hereinafter, the alkyl group may be represented by R.

Examples of the aminosilane-based gas may include a dimethylaminotrimethylsilane ((CH₃)₂NSi(CH₃)₃, abbreviation: DMATMS) gas, a diethylaminotrimethylsilane ((C₂H₅)₂NSi(CH₃)₃, abbreviation: DEATMS) gas, a diethylaminotriethylsilane ((C₂H₅)₂NSi(C₂H₅)₃, abbreviation: DEATES) gas, a dimethylaminotriethylsilane ((CH₃)₂NSi(C₂H₅)₃, abbreviation: DMATES) gas, and the like. In addition, not only one amino group (a dimethylamino group or a diethylamino group) but also three alkyl groups (methyl groups or ethyl groups) are bonded to Si which is the central atom of DMATMS, DEATMS, DEATES, DMATES, and the like. That is, DMATMS, DEATMS, DEATES, DMATES, and the like contain one amino ligand and three alkyl ligands.

As the aminosilane-based gas, in addition to these, a gas of an aminosilane compound represented by the following formula [1] may be used.

SiA_(x)[(NB₂)_((4-x))]  [1]

In the chemical formula [1], “A” represents a H atom, an alkyl group, or an alkoxy group, “B” represents a H atom or an alkyl group, and “x” represents an integer of 1 to 3. The alkyl group represented by “A” may be specifically an alkyl group containing 1 to 5 carbon atoms in some embodiments, more specifically an alkyl group containing 1 to 4 carbon atoms in some embodiments. The alkyl group represented by “A” may have a straight-chain form or a branched form. Examples of the alkyl group represented by “A” may include a methyl group, an ethyl group, a n-propyl group, a n-butyl group, an isopropyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and the like. The alkoxy group represented by “A” may be specifically an alkoxy group containing 1 to 5 carbon atoms in some embodiments, more specifically an alkoxy group containing 1 to 4 carbon atoms in some embodiments. An alkyl group in the alkoxy group represented by “A” is the same as the alkyl group represented by “A.” When x is 2 or 3, two or three A's may be the same or different. The alkyl group represented by “B” is the same as the alkyl group represented by “A.” Further, two B's may be the same or different, and when x is 1 or 2, a plurality of (NB2) may be the same or different. Further, the two B's may be bonded to form a ring structure, and the formed ring structure may further contain a substituent such as an alkyl group.

Examples of the aminosilane-based gas represented by the formula [1] may include a monoaminosilane (SiH₃(NR₂), abbreviation: MAS) gas in which in the formula [1], A is a H atom, B is an alkyl group, and x is 3 (that is, an aminosilane compound containing one amino group in one molecule), a bisaminosilane (SiH₂(NR₂)₂, abbreviation: BAS) gas in which in the formula [1], A is a H atom, B is an alkyl group, and x is 2 (that is, an aminosilane compound containing two amino groups in one molecule), and a trisaminosilane (SiH(NR₂)₃, abbreviation: TAS) gas in which in the formula [1], A is a H atom, B is an alkyl group, and x is 1 (that is, an aminosilane compound containing three amino groups in one molecule). Above all, the MAS gas may be used as the aminosilane-based gas. By using the MAS gas as the first gas, the surface of the base 200 a may be modified more uniformly and sufficiently in step A.

Examples of the MAS gas may include an ethylmethylaminosilane (SiH₃[N(CH₃)(C₂H₅)]) gas, a dimethylaminosilane (SiH₃[N(CH₃)₂]) gas, a diisopropylaminosilane (SiH₃[N(C₃H₇)₂]) gas, a disecondarybutylaminosilane (SiH₃[H(C₄H₉)₂]) gas, a dimethylpiperidinosilane (SiH₃[NC₅H₈(CH₃)₂]) gas, a diethylpiperidinosilane (SiH₃[NC₅H₈(C₂H₅)₂]) gas, and the like. One or more selected from the group of these gases may be used as the MAS gas. In the present disclosure, the MAS gas may be any gas of an aminosilane compound containing one amino group in one molecule and also includes those having a structure other than the structure represented by SiH₃(NR₂). For example, since the above-mentioned DMATMS, DEATMS, DEATES, and DMATES are also aminosilane compounds containing one amino group in one molecule, they may also be included in the MAS gas. The above-mentioned DMATMS, DEATMS, DEATES, and DMATES are aminosilane compounds in which in the formula [1], A is an alkyl group, B is an alkyl group, and x is 3.

An example of the Si-containing gas exemplified as an example of the first gas may include a halosilane-based gas which is a gas containing Si and a halogeno group. The halogeno group may include at least one selected from the group of a fluoro group, a chloro group, a bromo group, and an iodine group in some embodiments, and may include the chloro group among them in some embodiments. That is, the halosilane-based gas may contain at least one selected from the group of fluorine (F), chlorine (Cl), bromine (Br), and iodine (I), and may contain Cl among them in some embodiments. Examples of the halosilane-based gas may include a chlorosilane-based gas such as a hexachlorodisilane (Si₂Cl₆) gas, a tetrachlorosilane (SiCl₄) gas, a trichlorosilane (SiHCl₃) gas, a dichlorosilane (SiH₂Cl₂) gas, and a monochlorosilane (SiH₃Cl) gas, a fluorosilane-based gas such as a tetrafluorosilane (SiF₄) gas and a difluorosilane (SiH₂F₂) gas, a bromosilane-based gas such as a tetrabromosilane (SiBr₄) gas and a dibromosilane (SiH₂Br₂) gas, an iodosilane-based gas such as a tetraiodosilane (SiI₄) gas and a diiodosilane (SiH₂I₂) gas, and the like. One or more selected from the group of these gases may be used as the halosilane-based gas.

Further, as the halosilane-based gas, an alkylhalosilane-based gas may be used. Examples of the alkylhalosilane-based gas may include an alkylchlorosilane-based gas such as a dimethyldichlorosilane ((CH₃)₂SiCl₂) gas and a trimethylchlorosilane ((CH₃)₃SiCl) gas, an alkylfluorosilane-based gas such as a dimethyldifluorosilane ((CH₃)₂SiF₂) gas and a trimethylfluorosilane ((CH₃)₃SiF) gas, an alkylbromosilane-based gas such as a dimethyldibromosilane ((CH₃)₂SiBr₂) gas and a trimethylbromosilane ((CH₃)₃SiBr) gas, an alkyliodosilane-based gas such as a dimethyldiiodosilane ((CH₃)₂SiI₂) gas and a trimethyliodosilane ((CH₃)₃SiI) gas, and the like. One or more selected from the group of these gases may be used as the alkylhalosilane-based gas.

An example of the Si-containing gas exemplified as an example of the first gas may include a gas containing Si and H, that is, a silicon hydride gas. Examples of the silicon hydride gas may include a monosilane (SiH₄) gas, a disilane (Si₂H₆) gas, a trisilane (Si₃H₈) gas, a tetrasilane (Si₄H₁₀) gas, and the like. One or more selected from the group of these gases may be used as the silicon hydride gas.

Examples of the metal-containing gas exemplified as an example of the first gas may include a gas containing metal and an amino group, a gas containing metal and a halogeno group, and the like. The halogeno group may include at least one selected from the group of a fluoro group, a chloro group, a bromo group, and an iodine group in some embodiments, and may include the chloro group among them in some embodiments. That is, the gas containing the metal and the halogeno group may contain at least one selected from the group of F, Cl, Br, and I in some embodiments, and may contain Cl in some embodiments. Examples of the metal-containing gas may include a tetrakis(dimethylamino)titanium (Ti[N(CH₃)₂]₄) gas, a tetrakis(diethylamino)titanium (Ti[N(C₂H₅)₂]₄) gas, a tetrafluorotitanium (TiF₄) gas, a tetrachlorotitanium (TiCl₄) gas, a tetrabromotitanium (TiBr₄) gas, a tetraiodotitanium (TiI₄) gas, and the like. One or more selected from the group of these gases may be used as the metal-containing gas.

Examples of the O-containing gas exemplified as an example of the first gas may include an oxygen (O₂) gas, a nitric oxide (NO) gas, a nitrogen dioxide (NO₂) gas, a nitrous oxide (N₂O) gas, an ozone (O₃) gas, water vapor (H₂O gas), a hydrogen peroxide (H₂O₂) gas, an O₂ gas+H₂ gas, an O gas+H₂ gas, and the like. One or more selected from the group of these gases may be used as the O-containing gas.

Examples of the N- and H-containing gas exemplified as an example of the first gas may include an ammonia (NH₃) gas, a hydrazine (N₂H₄) gas, a diazene (N₂H₂) gas, a monomethylhydrazine (CH₃HN₂H₂) gas, a dimethylhydrazine ((CH₃)₂N₂(CH₃)H) gas, a trimethylhydrazine ((CH₃)₃N₂H₂) gas, and the like. One or more selected from the group of these gases may be used as the N- and H-containing gas.

Examples of the B-containing gas and the P-containing gas exemplified as examples of the first gas may include a B- and H-containing gas, a P- and H-containing gas, and the like. Examples of these gases may include a diborane (B₂H₆) gas, a phosphine (PH₃) gas, and the like. One or more selected from the group of these gases may be used.

Examples of the halogen-containing gas exemplified as an example of the first gas may include a C- and F-containing gas, a Cl- and F-containing gas, a F-containing gas, a N- and F-containing gas, a N-, F-, and O-containing gas, a N-, Cl-, and O-containing gas, and the like. Examples of these gases may include a tetrafluoromethane (CF₄) gas, a hexafluoroethane (C₂F₆) gas, an octafluoropropane (C₃F₈) gas, a chlorine monofluoride (ClF) gas, a chlorine trifluoride (ClF₃) gas, a fluorine (F₂) gas, a nitrogen trifluoride (NF₃) gas, a nitrosyl fluoride (FNO) gas, a nitrosyl trifluoride (F₃NO) gas, a nitroyl fluoride (FNO₂) gas, a nitrosyl chloride (ClNO) gas, a NF₃ gas+NO gas, a F₂ gas+NO gas, a ClF gas+NO gas, a ClF₃ gas+NO gas, and the like. One or more selected from the group of these gases may be used.

In the present disclosure, the description of two gases such as “NF₃ gas+NO gas” together means a mixture of NF₃ gas and NO gas. When supplying the mixture, the two gases may be mixed (pre-mixed) in a supply pipe and then supplied into the process chamber 201, or the two gases may be supplied separately from different supply pipes into the process chamber and then mixed (post-mixed) in the process chamber 201.

Further, in some embodiments, a gas that is difficult to store, such as the FNO gas, may be generated by mixing a F₂ gas and a NO gas in a supply pipe or a nozzle installed in the substrate processing apparatus, and the FNO gas generated in the supply pipe or the nozzle may be supplied into the process chamber 201. Further, for example, a gas mixing chamber may be installed in the substrate processing apparatus, the F₂ gas and the NO gas may be mixed in the gas mixing chamber to generate the FNO gas, and the FNO gas generated in the gas mixing chamber may be supplied into the process chamber 201 via the supply pipe or the nozzle.

Examples of the inert gas used in step A may include, in addition to the nitrogen (N₂) gas, a rare gas such as an argon (Ar) gas, a helium (He) gas, a neon (Ne) gas, and a xenon (Xe) gas. As the inert gas, the same gas may be used in each step to be described below.

Step B

In step B, after step A is completed, a second gas is supplied to the wafer 200 in the process chamber 201, that is, to the wafer 200 where the first modified layer 200 b is formed on the surface of the base 200 a. As described above, the second gas is a gas having a molecular structure different from that of the first gas.

Specifically, the valve 243 b is opened to allow the second gas to flow into the gas supply pipe 232 b. A flow rate of the second gas is regulated by the MFC 24 lb. Then, the second gas is supplied into the process chamber 201 via the nozzle 249 b, flows over the surface of the wafer 200, and is exhausted via the exhaust port 231 a. In this operation, the second gas is supplied to the wafer 200. Further, at this time, the valves 243 d to 243 f may be opened to allow an inert gas to be supplied into the process chamber 201 via the nozzles 249 a to 249 c, respectively.

By supplying the second gas to the wafer 200 under conditions to be described below, the etching species is generated from the first modified layer 200 b formed on the surface of the base 200 a. Specifically, as shown in FIG. 5B, when the second gas 20 is supplied to the wafer 200 where the first modified layer 200 b is formed on the surface of the base 200 a, the first modified layer 200 b (here, the first gas 10 adsorbed on the surface of the base 200 a) is activated by the second gas 20 to generate the etching species 200 c, as shown in FIG. 5C.

The etching species 200 c is generated by at least one selected from the group of causing the second gas to react with the first modified layer 200 b and activating the first modified layer 200 b with the second gas. The generation of the etching species 200 c as in the former may be referred to as generation of the etching species by reaction. The generation of the etching species 200 c as in the latter may be referred to as generation of the etching species by activation. That is, in this step, the etching species 200 c is generated on the surface of the base 200 a by the generation of the etching species by the reaction and/or the generation of the etching species by the activation. Since the etching species 200 c is generated with the first modified layer 200 b formed in a layer form being as the base and exists in a layer form, the etching species 200 c may be referred to as a layer 200 c containing the etching species, an etching species-containing layer 200 c, or simply an etching species layer 200 c. FIG. 5C shows, as an example, an etching species 200 c generated by activating the first gas 10 adsorbed on the surface of the base 200 a with the second gas 20, that is, a layer 200 c containing the etching species.

When the etching species 200 c is generated on the surface of the base 200 a, a portion of the surface of the base 200 a is etched by the etching species 200 c, as shown in FIG. 5D. When the portion of the surface of the base 200 a is etched by the etching species 200 c, for example, a first product 12, which is a by-product, is produced in the process of the etching reaction, as shown in FIG. 5D. At this time, as a by-product, a second product 14 may be produced in addition to the first product 12. Hereinafter, a case where the first product 12 and the second product 14 are produced as by-products will be described.

When the portion of the surface of the base 200 a is etched by the etching species 200 c, and when the first product 12 and the second product 14 which are the by-products are produced, for example, the first product 12 is desorbed from the surface of the base 200 a, as shown in FIG. 5E. At this time, the second product 14 remains on the surface of the base 200 a. In addition, at this time, a portion of the second product 14 may be desorbed from the surface of the base 200 a. Further, at this time, the second product 14 may exhibit a behavior in which desorption from the surface of the base 200 a and adsorption on the surface of the base 200 a are performed one or more time. FIG. 5E shows, as an example, the desorption of the second product 14 from the surface of the base 200 a and the adsorption of the second product 14 on the surface of the base 200 a. Then, as shown in FIG. 5F, the second product 14 is in a state where the second product 14 uniformly remains and/or is adsorbed in the surface of the base 200 a whose surface is partially etched.

In this way, when the second product 14 uniformly remains and/or is adsorbed in the surface of the base 200 a whose surface is partially etched, at least one selected from the group of the second product 14, the second gas 20, and the base 200 a whose surface is partially etched reacts to form a second modified layer 200 d on the surface of the base 200 a whose surface is partially etched, as shown in FIG. 5G. For example, the second modified layer 200 d may be formed by reacting the second product 14 and the second gas 20 with the base 200 a whose surface is partially etched. Further, for example, the second modified layer 200 d may be formed by reacting the second product 14, the second gas 20, and the base 200 a whose surface is partially etched.

In a case where the base 200 a is a silicon-based nitrogen-containing film such as a SiN film and at least one selected from the group of the first gas and the second gas is the above-mentioned halogen-containing gas, the first modified layer 200 b may become an adsorption layer of halogen-containing gas. In this case, as the first product 12, for example, a substance containing at least one selected from the group of nitrogen, halogen, and silicon may be produced, and as the second product 14, for example, a substance containing at least one selected from the group of nitrogen, oxygen, silicon, and halogen may be produced. Further, in this case, the second modified layer 200 d may become a substance containing silicon, oxygen, and halogen.

As described above, in this step, the second product 14 may not be produced as the by-product. In this case, the second modified layer 200 d may not formed on the surface of the base 200 a whose surface is partially etched.

As described above, in this step, the etching species 200 c is generated with the first modified layer 200 b being as the base by the second gas, and a portion of the surface of the base 200 a is etched by the generated etching species 200 c. By undergoing such a process, it is possible to improve the controllability of the etching amount when etching the base 200 a.

This is because this method is not a method of directly etching a film to be etched (here, the base 200 a) with an etching gas, but is hard to be affected by a distribution of gas partial pressure (supply amount) due to a shape of the film to be etched.

In this method, the etching amount of the base 200 a may be controlled by controlling an amount of the etching species 200 c generated in step B. Further, the amount of the etching species 200 c may be controlled by the adsorption amount of the first gas on the surface of the base 200 a in step A and the amount of the compound generated on the surface of the base 200 a in step A. That is, the amount of the etching species 200 c may be controlled by an amount of the first modified layer 200 b formed in step A, that is, a thickness of the first modified layer 200 b, that is, a modification amount of the base 200 a in step A. Then, in step A, the first modified layer 200 b is uniformly formed in the surface of the base 200 a, so that in step B, the etching species may be uniformly generated in the surface of the base 200 a, which makes it possible to improve the uniformity of the etching amount of the base 200 a. This enables a conformal etching process.

Further, as described above, in step A, a self-limit may be generated in the reaction by which the first modified layer 200 b is formed. That is, in step A, the modification reaction by adsorption may be saturated, and the modification reaction by compound generation may also be saturated. By saturating the reaction by which the first modified layer 200 b is formed, the first modified layer 200 b may be formed more uniformly in the surface of the base 200 a. As a result, in step B, the etching species may be generated more uniformly in the surface of the base 200 a, so that the uniformity of the etching amount of the base 200 a may be further improved. This enables a further conformal etching process. As a method of saturating this modification reaction, the method of saturating the modification reaction by adsorption can provide a controllability of the etching amount higher than that of the method of saturating the modification reaction by compound generation.

As described above, the amount of the etching species 200 c generated in step B depends on the amount of the first modified layer 200 b formed in step A. That is, in step B, after the generation reaction of the etching species 200 c with the first modified layer 200 b being as the base is completed, the etching species 200 c is not generated even though the second gas is further supplied. That is, in step B, after the entire first modified layer 200 b is converted into the etching species, or after a component to be converted into the etching species disappears in the first modified layer 200 b, the etching species 200 c is not generated even though the second gas is further increased. In this way, in this method, not only the modification reaction in step A may be saturated, but also the generation reaction of the etching species 200 c in step B may be saturated. The modification reaction in step A and/or the generation reaction of the etching species 200 c in step B may be made unsaturated, which makes it possible to control the etching amount more precisely and finely.

After the etching of the portion of the surface of the base 200 a by the etching species 200 c is completed and the second modified layer 200 d is formed on the surface of the base 200 a whose surface is partially etched, the valve 243 b is closed to stop the supply of the second gas 20 into the process chamber 201. Then, according to the same processing sequence as the purge in step A, the interior of the process chamber 201 is vacuum-evacuated to remove a gas and the like remaining in the process chamber 201 from the interior of the process chamber 201. At this time, as in step A, the valves 243 d to 243 f may be opened to allow an inert gas to be supplied into the process chamber 201 via the nozzles 249 a to 249 c, thereby performing the purging with the inert gas. By the above purging, the second modified layer 200 d is left on the surface of the base 200 a whose surface is partially etched, and the second gas and the like remaining in the process chamber 201 are removed.

A process condition when the second gas is supplied in step B is exemplified as follows:

Processing temperature: 25 to 400 degrees C., specifically 50 to 250 degrees C.

Processing pressure: 1 to 13,300 Pa, specifically 50 to 2,660 Pa

Second gas supply flow rate: 1 to 5,000 sccm, specifically 50 to 2,000 sccm

Second gas supply time: 1 to 3,000 seconds, specifically 10 to 1,200 seconds

Inert gas supply flow rate (for each gas supply pipe): 100 to 5,000 sccm, specifically 100 to 3,000 sccm

In the aforementioned process condition, by setting the processing temperature to 25 degrees C. or higher, specifically 50 degrees C. or higher, it is possible to generate the etching species by reaction and/or the etching species by activation. Further, in the aforementioned process condition, by setting the processing temperature to 400 degrees C. or lower, specifically 250 degrees C. or lower, the etching of the first film (the base 200 a) by the etching species 200 c may be promoted while suppressing the direct etching of the first film (the base 200 a) by the second gas 20.

When the second gas is present alone, the aforementioned process condition may be a condition under which the etching reaction of the base 200 a is difficult to continue. Further, when the first gas is present alone, the aforementioned process condition may be a condition under which the etching reaction of the base 200 a is difficult to continue.

In this step, the second gas is supplied to the wafer 200 under a condition that the reaction between the second gas and the first modified layer 200 b is predominantly generated (predominant) over the reaction between the second gas and the base 200 a. This makes it possible to promote the generation of the etching species that contributes to the etching of the base 200 a while suppressing the direct etching of the base 200 a with the second gas. As a result, it is possible to further improve the controllability of the etching amount when etching the base 200 a. In the aforementioned process condition, for example, by setting the processing temperature to a predetermined temperature of 400 degrees C. or lower, specifically 250 degrees C. or lower, the second gas may be supplied to the wafer 200 under the condition that the reaction between the second gas and the first modified layer 200 b is predominantly generated over the reaction between the second gas and the base 200 a.

Further, in this step, under the condition that the reaction between the second gas and the first modified layer 200 b progresses and the reaction between the second gas and the base 200 a does not progress, the second gas may be supplied to the wafer 200. This makes it possible to promote the generation of the etching species that contributes to the etching of the base 200 a while reliably suppressing the direct etching of the base 200 a with the second gas. As a result, it is possible to further improve the controllability of the etching amount when etching the base 200 a. In the aforementioned process condition, for example, by setting the processing temperature to a predetermined temperature of 250 degrees C. or lower, specifically 200 degrees C. or lower, more specifically 150 degrees C. or lower, the second gas may be supplied to the wafer 200 under the condition that the reaction between the second gas and the first modified layer 200 b progresses and the reaction between the second gas and the base 200 a does not progress.

Further, in this step, the second gas is supplied to the wafer 200 under a condition that the activation of the first modified layer 200 b by the second gas is predominantly generated over the activation of the base 200 a by the second gas. This makes it possible to promote the generation of the etching species that contributes to the etching of the base 200 a while suppressing the direct etching of the base 200 a with the second gas. As a result, it is possible to further improve the controllability of the etching amount when etching the base 200 a. In the aforementioned process condition, for example, by setting the processing temperature to a predetermined temperature of 400 degrees C. or lower, specifically 250 degrees C. or lower, the second gas may be supplied to the wafer 200 under the condition that the activation of the first modified layer 200 b by the second gas is predominantly generated over the activation of the base 200 a by the second gas.

Further, in this step, the second gas may be supplied to the wafer 200 under a condition that the activation of the first modified layer 200 b by the second gas progresses and the activation of the base 200 a by the second gas does not progress. This makes it possible to promote the generation of the etching species that contributes to the etching of the base 200 a while reliably suppressing the direct etching of the base 200 a with the second gas. As a result, it is possible to further improve the controllability of the etching amount when etching the base 200 a. In the aforementioned process condition, for example, by setting the processing temperature to a predetermined temperature of 250 degrees C. or lower, specifically 200 degrees C. or lower, more specifically 150 degrees C. or lower, the second gas may be supplied to the wafer 200 under the condition that the activation of the first modified layer 200 b by the second gas progresses and the activation of the base 200 a by the second gas does not progress.

Further, in this step, the second gas is supplied to the wafer 200 under a condition that the etching of the base 200 a by the etching species progress more than the reaction between the second gas and the base 200 a. This makes it possible to suppress the direct etching of the base 200 a with the second gas, such that the etching reaction of the base 200 a by the etching species is generated predominantly. As a result, it is possible to further improve the controllability of the etching amount when etching the base 200 a. In the aforementioned process condition, for example, by setting the processing temperature to a predetermined temperature of 400 degrees C. or lower, specifically 250 degrees C. or lower, the second gas may be supplied to the wafer 200 under the condition that the etching of the base 200 a by the etching species progresses more than the reaction between the second gas and the base 200 a.

Further, in the processing condition at this step, under the condition that the etching of the base 200 a by the etching species progresses and the reaction between the second gas and the base 200 a does not progress, the second gas may be supplied to the wafer 200. As a result, it is possible to reliably suppress the direct etching of the base 200 a with the second gas, such that the etching reaction of the base 200 a by the etching species is generated more predominantly. As a result, it is possible to further improve the controllability of the etching amount when etching the base 200 a. In the aforementioned process condition, for example, by setting the processing temperature to a predetermined temperature of 250 degrees C. or lower, specifically 200 degrees C. or lower, more specifically 150 degrees C. or lower, under the condition that the etching of the base 200 a by the etching species progresses and the reaction between the second gas and the base 200 a does not progress, the second gas may be supplied to the wafer 200.

Further, as described above, in this step, under the condition that the generation reaction of the etching species 200 c may be saturated, the second gas may be supplied to the wafer 200. For example, by setting the processing temperature to a predetermined temperature of 400 degrees C. or lower, specifically 250 degrees C. or lower, the generation reaction of the etching species 200 c may be saturated. Further, for example, even when the processing temperature is set to a predetermined temperature of 200 degrees C. or lower or 150 degrees C. or lower, the generation reaction of the etching species 200 c may be saturated. Further, as described above, in this step, after the entire first modified layer 200 b is converted into the etching species, or after the component to be converted into the etching species disappears in the first modified layer 200 b, since the etching species 200 c is not generated, the generation reaction of the etching species 200 c is relatively easy to be saturated. However, even when the processing temperature is set to such a temperature, the generation reaction of the etching species 200 c may be unsaturated by regulating conditions other than the processing temperature (for example, shortening the second gas supply time, lowering the processing pressure, and the like).

A process condition under which the purging with the inert gas is performed in step B is exemplified as follows:

Processing temperature: 25 to 400 degrees C., specifically 50 to 250 degrees C.

Processing pressure: 1 to 13,300 Pa, specifically 50 to 1,330 Pa

Inert gas supply flow rate (for each gas supply pipe): 100 to 5,000 sccm, specifically 500 to 3,000 sccm

Inert gas supply time: 1 to 600 seconds, specifically 10 to 120 seconds

The second gas used in step B is not particularly limited as long as it is a gas capable of reacting with the first modified layer 200 b and/or activating the first modified layer 200 b to generate the etching species.

Examples of the second gas may include a halogen-containing gas, an acetylacetone-based gas, and the like. Examples of the halogen-containing gas and the acetylacetone-based gas may include an I- and F-containing gas, a B- and Cl-containing gas, a Cl-containing gas, a H- and Cl-containing gas, a S-, O-, and Cl-containing gas, a H- and F-containing gas, a metal- and F-containing gas, a metal- and Cl-containing gas, a Cl- and F-containing gas, a F-containing gas, a N- and F-containing gas, a N-, F-, and O-containing gas, a N-, Cl-, and O-containing gas, a C-, H-, and O-containing gas, a C-, H-, F-, and O-containing gas, and the like.

Examples of these gases may include an iodine heptafluoride (IFS) gas, an iodine pentafluoride (IF₅) gas, a boron trichloride (BCl₃) gas, a chlorine (Cl₂) gas, a hydrogen chloride (HCl) gas, a thionyl chloride (SOCl₂) gas, a hydrogen fluoride (HF) gas, a tungsten hexafluoride (WF₆) gas, a tungsten hexachloride (WCl₆) gas, a tungsten pentafluoride (WCl₅) gas, a chlorine monofluoride (ClF) gas, a chlorine trifluoride (ClF₃) Gas, a fluorine (F₂) gas, a nitrogen trifluoride (NF₃) gas, a nitrosyl fluoride (FNO) gas, a nitrosyl trifluoride (F₃NO) gas, a nitroyl fluoride (FNO₂) gas, a nitrosyl chloride (ClNO) gas, an acetylacetone (C₅H₈O₂) gas, a hexafluoroacetylacetone (C₅H₂F₆O₂) gas, and the like. One or more selected from the group of these gases can be used as the halogen-containing gas and the acetylacetone-based gas.

Further, as described above, a gas such as the FNO gas that is difficult to store may be generated by mixing a F₂ gas and a NO gas in a supply pipe or a nozzle installed in the substrate processing apparatus, and the FNO gas generated in the supply pipe or the nozzle may be supplied into the process chamber 201. Further, as described above, for example, a gas mixing chamber may be installed in the substrate processing apparatus, the F₂ gas and the NO gas may be mixed in the gas mixing chamber to generate the FNO gas, and the FNO gas generated in the gas mixing chamber may be supplied into the process chamber 201 via the supply pipe or the nozzle.

Step A in at Least One Subsequent Cycle

As described previously, in step B, the second modified layer 200 d may be formed on the surface of the base 200 a whose surface is partially etched. In this case, in step A in at least one subsequent cycle, the first gas is supplied to the wafer 200 in the process chamber 201, that is, the wafer 200 where the second modified layer 200 d is formed on the surface of the base 200 a whose surface is partially etched. A supply method and supply conditions of the first gas may be the same as those in step A described above.

Under the above-mentioned conditions, by supplying the first gas to the wafer 200 in which the second modified layer 200 d is formed on the surface of the base 200 a whose surface is partially etched, the first gas 10 is adsorbed on the surface of the second modified layer 200 d, as shown in FIG. 5H. When the first gas 10 is adsorbed on the surface of the second modified layer 200 d, the first gas 10 reacts with the second modified layer 200 d to remove the second modified layer 200 d, as shown in FIG. 5I. In the process of the reaction between the first gas 10 and the second modified layer 200 d, the product 30, which is the by-product, is produced and adsorbed on the surface of the base 200 a from which the second modified layer 200 d has been removed. The product 30 may be, for example, the same substance as the first product 12.

By continuing the supply of the first gas 10 to the wafer 200 even after the product 30 is adsorbed on the surface of the base 200 a, the product 30 is desorbed from the surface of the base 200 a, as shown in FIG. 5J. Then, after the product 30 is desorbed from the surface of the base 200 a, the surface of the base 200 a is exposed again, as shown in FIG. 5K.

Then, even after the base 200 a is exposed again, by continuing the supply of the first gas 10 to the wafer 200, the first gas 10 is adsorbed on the surface of the base 200 a to form a first modified layer 200 b, as in the state shown in FIG. 5A. The subsequent processes are performed in the same manner as in the first cycle, and a reaction similar to that in the first cycle occurs.

In step B, in a case where the second product 14 is not produced as the by-product, the second modified layer 200 d is not formed on the surface of the base 200 a whose surface is partially etched. In this case, the same reaction as in step A in the first cycle occurs even in step A in the at least one subsequent cycle.

Performing Predetermined Number of Times

When a cycle that non-simultaneously (that is, asynchronously) performs the above-described steps A and B is performed a predetermined number of times (n times, where n is an integer of 1 or more), the base 200 a exposed on the surface of the wafer 200 may be etched to a desired depth. The aforementioned cycle may be performed multiple times. That is, a thickness of a layer etched per one cycle may be set to be smaller than a desired thickness. Thus, the aforementioned cycle may be performed multiple times until the thickness of the layer removed by etching becomes equal to the desired thickness.

After-Purge and Returning to Atmospheric Pressure

After the etching process of the base 200 a is completed, an inert gas as a purge gas is supplied into the process chamber 201 from each of the nozzles 249 a to 249 c and is exhausted through the exhaust port 231 a. Thus, the interior of the process chamber 201 is purged to remove a gas and reaction by-products remaining in the process chamber 201 from the interior of the process chamber 201 (after-purge). Thereafter, the internal atmosphere of the process chamber 201 is substituted with an inert gas (inert gas substitution) and the internal pressure of the process chamber 201 is returned to the atmospheric pressure (returning to atmospheric pressure).

Boat Unloading and Wafer Discharging

The seal cap 219 is moved down by the boat elevator 115 to open the lower end of the manifold 209. Then, the processed wafers 200 supported by the boat 217 are unloaded from the lower end of the manifold 209 to the outside of the reaction tube 203 (boat unloading). After the boat unloading, the shutter 219 s is moved such that the lower end opening of the manifold 209 is sealed by the shutter 219 s via the O-ring 220 c (shutter closing). The processed wafers 200 are unloaded to the outside of the reaction tube 203, and then are subsequently discharged from the boat 217 (wafer discharging).

(3) Effects of the Embodiments

According to the embodiments of the present disclosure, one or more effects described below may be achieved.

By performing a cycle a predetermined number of times, the cycle including non-simultaneously step A and step B, to etch the base 200 a, the controllability of the etching amount of the base 200 a may be improved. That is, instead of directly etching the base 200 a with the first gas or the second gas, the base 200 a is etched with the etching species 200 c generated on the surface of the base 200 a in step B. As a result, it is possible to make it less likely to be affected by the distribution of the gas partial pressure (=supply amount) due to the shape of the base 200 a, thereby improving the controllability of the etching amount of the base 200 a. In this case, by controlling the amount of the etching species 200 c generated on the surface of the base 200 a in step B, it is possible to freely control the etching amount of the base 200 a. For example, it is possible to control the etching amount of the base 200 a to a level of one atomic layer (one molecular layer) or less, and it is also possible to control the etching amount of the base 200 a to a level exceeding one atomic layer (one molecular layer), for example, several atomic layers (several molecular layers). The level at which the etching amount is one atomic layer (one molecular layer) or less means a level at which the etching thickness is one atomic layer (one molecular layer) or less than one atomic layer (one molecular layer). The level at which the etching amount is less than one atomic layer (one molecular layer) means a level at which the etching thickness does not reach one atomic layer (one molecular layer). For example, such a level applies to a case where the etching amount is a half-atomic layer (half-molecular layer), and the like. Further, according to this method, the etching amount may be controlled to be at a level of the half-atomic layer (half-molecular layer) or less, that is, the half-atomic layer (half-molecular layer) or less than the half-atomic layer (half-molecular layer).

Even under a situation where an amount of exposure of a gas is likely to be locally reduced or a situation where a gas partial pressure in the process chamber 201 is not constant depending on the location, for example, when a 3D structure such as a trench or a hole is formed on the surface of the wafer 200 and the base 200 a is provided along the surface shape of the wafer 200, by etching the base 200 a by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing step A and step B, it is possible to control the etching amount of the base 200 a finely so as to be uniform over the surface of the wafer 200. This enables a conformal etching process.

When at least one selected from the group of the first gas and the second gas is present alone, under the condition that the etching reaction of the base 200 a is difficult to continue, the cycle including non-simultaneously performing step A and step B may be performed a predetermined number of times to realize the aforementioned effects in some embodiments. Further, when each of the first gas and the second gas is present alone, under the condition that the etching reaction of the base 200 a is difficult to continue, the cycle including non-simultaneously performing step A and step B may be performed a predetermined number of times in some embodiments.

In step A, since a portion where the first modified layer 200 b is formed becomes the base of the etching species 200 c to be generated on the surface of the base 200 a in step B, it is possible to control the amount of the etching species 200 c generated in step B, that is, the etching amount, with the adsorption amount of the first gas on the surface of the base 200 a in step A.

For example, in step A, by setting the thickness of the adsorption layer of the first gas (that is, the first modified layer 200 b, the same applies hereinafter) formed on the surface of the base 200 a to one atomic layer (one molecular layer) or less, it is possible to control the etching amount (etching thickness) of the base 200 a in step B to a level of, for example, one atomic layer (one molecular layer) or less. Further, for example, in step A, by setting the thickness of the adsorption layer of the first gas formed on the surface of the base 200 a to less than one atomic layer (one molecular layer), it is possible to control the etching amount of the base 200 a in step B to a level of, for example, less than one atomic layer (one molecular layer). Further, for example, in step A, by setting the thickness of the adsorption layer of the first gas formed on the surface of the base 200 a set to a thickness exceeding one atomic layer (one molecular layer), it is possible to control the etching amount of the base 200 a in step B to a level exceeding, for example, one atomic layer (one molecular layer). Further, for example, in step A, by setting the thickness of the adsorption layer of the first gas formed on the surface of the base 200 a to several atomic layers (several molecular layers), it is possible to control the etching amount of the base 200 a in step B to a level of, for example, several atomic layers (several molecular layers).

Since the portion where the first modified layer 200 b is formed in step A becomes the base of the etching species 200 c generated on the surface of the base 200 a in step B, it is possible to control the amount of the etching species 200 c generated in step B, that is, the etching amount, by the amount of a compound generated on the surface of the base 200 a in step A.

For example, in step A, by setting the thickness of the compound generated on the surface of the base 200 a to one atomic layer (one molecular layer) or less, it is possible to control the etching amount (etching thickness) of the base 200 a in step B to a level of, for example, one atomic layer (one molecular layer) or less. Further, for example, in step A, by setting the thickness of the compound generated on the surface of the base 200 a to less than one atomic layer (one molecular layer), it is possible to control the etching amount of the base 200 a in step B to a level of, for example, less than one atomic layer (one molecular layer). Further, for example, in step A, by setting the thickness of the compound generated on the surface of the base 200 a set to a thickness exceeding one atomic layer (one molecular layer), it is possible to control the etching amount of the base 200 a in step B to a level exceeding, for example, one atomic layer (one molecular layer). Further, for example, in step A, by setting the thickness of the compound generated on the surface of the base 200 a to several atomic layers (several molecular layers), it is possible to control the etching amount of the base 200 a in step B to a level of, for example, several atomic layers (several molecular layers).

In step A, the reaction by which the first modified layer 200 b is formed, that is, the modification reaction, may be saturated. This allows the first modified layer 200 b to formed more uniformly in the surface of the base 200 a in step A. As a result, in step B, the etching species may be generated more uniformly in the surface of the base 200 a, thereby further improving the uniformity of the etching amount of the base 200 a. This enables a further conformal etching process. As a method of saturating this modification reaction, the method of saturating the modification reaction by adsorption can provide a controllability of the etching amount higher than that of the method of saturating the modification reaction by compound generation. For example, in step A, by saturating the modification reaction by adsorption, the thickness of the adsorption layer of the first gas formed on the surface of the base 200 a may be easily set to one atomic layer (one molecular layer) or less.

In step B, not only the portion of the surface of the base 200 a is etched, but also the second modified layer 200 d that can be removed by the first gas may be formed on the surface of the base 200 a whose surface has been partially etched. In this case, in step A in the at least one subsequent cycle, the second modified layer 200 d is removed by supplying the first gas to the wafer 200, and the first modified layer 200 b may be formed on the surface of the base 200 a exposed by removing the second modified layer 200 d. That is, in step A in the at least one subsequent cycle, the second modified layer 200 d formed in step B may be removed, and the first modified layer 200 b may be formed on the surface of the base 200 a. This makes it possible to improve a total etching rate of the base 200 a when the cycle including non-simultaneously performing step A and step B is performed one or more times.

The first gas may include one or more selected from the group of the above-mentioned gases exemplified as the first gas, and the second gas may include one or more selected from the group of the above-mentioned gases exemplified as the second gas. However, the first gas and the second gas need to be gases having different molecular structures. When the first gas and the second gas are in such a combination, the aforementioned effects may be particularly exhibited.

The controllability of the etching amount may be further improved by performing, under a non-plasma atmosphere, the process of etching the base 200 a by performing a cycle a predetermined number of times, the cycle including non-simultaneously performing step A and step B. Further, by performing this etching process under the non-plasma atmosphere, it is possible to prevent damage to the wafer 200 and a film formed on the surface of the wafer 200 due to plasma.

Other Embodiments of the Present Disclosure

The embodiments of the present disclosure have been described above in detail. However, the present disclosure is not limited to the aforementioned embodiments, but may be differently modified without departing from the subject matter of the present disclosure.

For example, the base 200 a as the first film to be etched may include at least one selected from the group of a silicon nitride film (SiN film), a silicon carbon nitride film (SiCN film), a nitrogen-rich silicon oxynitride film (SiON film), a nitrogen-rich silicon oxycarbonitride film (SiOCN film), a silicon boron nitride film (SiBN film), a silicon borocarbonitride film (SiBCN film), a boron nitride film (BN film), a titanium nitride film (TiN film), a tungsten nitride film (WN film), a tungsten film (W film), a molybdenum film (Mo film), a silicon film (Si film), a germanium film (Ge film), and a silicon germanium film (SiGe film).

Further, the O-containing film such as the SiON film or the SiOCN film as the first film may be a N-rich film, that is, a film having a higher N concentration in the film than an O concentration in the film in some embodiments. That is, the SiON film and the SiOCN film may be a N-rich SiON film and a N-rich SiOCN film, respectively, in some embodiments. Even in a case where the first film contains O in addition to N, when the N concentration is higher than the O concentration, the first film may be sufficiently etched with the method according to the aforementioned embodiments.

In this way, the base 200 a as the first film may be a nitrogen-containing film such as a silicon-based nitride film (silicon-based nitrogen-containing film) such as a SiN film, a SiCN film, a N-rich SiON film, a N-rich SiOCN film, a SiBN film, or a SiBCN film, a boron-based nitride film (boron-based nitrogen-containing film) such as a BN film, or a metal-based nitride film (metal-based nitrogen-containing film) such as a TiN film or a WN film, a metal film (transition metal film or transition metal single film) such as a W film or a Mo film, or a semiconductor film such as a Si film, a Ge film, or a SiGe film.

Even when the base 200 a as the first film is at least one selected from the group of these films, the same effects as those in the above-described embodiment may be achieved.

Further, for example, as in a processing sequence described below, a pre-process (step C) of supplying a third gas to the wafer 200 may be performed before the first gas is supplied to the wafer 200. This makes it possible to promote the formation of the first modified layer 200 b on the surface of the base 200 a exposed on the surface of the wafer 200, for example.

(Third gas→First gas→Second gas)×n

Hereinafter, a processing sequence and a process condition in step C will be described. Processing sequences and processing conditions other than those in step C may be the same as those described above.

Step C

In step C, the third gas is supplied to the wafer 200 in the process chamber 201, that is, to the wafer 200 having a surface on which the base 200 a as the first film is exposed.

Specifically, the valve 243 c is opened to allow the third gas to flow into the gas supply pipe 232 c. A flow rate of the third gas is regulated by the MFC 241 c, and then the third gas is supplied into the process chamber 201 via the nozzle 249 c, flows over the surface of the wafer 200, and is exhausted via the exhaust port 231 a. In this operation, the third gas is supplied to the wafer 200. Further, at this time, the valves 243 d to 243 f may be opened to allow the inert gas to be supplied into the process chamber 201 via the nozzles 249 a to 249 c, respectively.

By supplying the third gas to the wafer 200 under conditions to be described below, it is possible to pre-process the surface of the base 200 a exposed on the surface of the wafer 200. For example, the surface of the base 200 a may be pre-processed so that the surface of the base 200 a functions as an adsorption site of the first gas.

After pre-processing the surface of the base 200 a, the valve 243 c is closed to stop the supply of the third gas into the process chamber 201. Then, the interior of the process chamber 201 is vacuum-evacuated to remove a gas or the like remaining in the process chamber 201 from the interior of the process chamber 201. At this time, the valves 243 d to 243 f are opened to allow an inert gas to be supplied into the process chamber 201 via the nozzles 249 a to 249 c. The inert gas supplied from the nozzles 249 a to 249 c acts as a purge gas, whereby the interior of the process chamber 201 is purged (purge). The purging with the inert gas may not be performed.

A process condition when the third gas is supplied in step C is exemplified as follows:

Processing temperature: 30 to 300 degrees C.

Processing pressure: 5 to 1,000 Pa

Third gas supply flow rate: 10 to 2,000 sccm

Third gas supply time: 5 to 1,800 seconds

Inert gas supply flow rate (for each gas supply pipe): 0 to 10,000 sccm

The third gas is not particularly limited as long as it is a gas capable of performing the aforementioned pre-process, that is, a gas capable of forming an adsorption site of the first gas on the surface of the base 200 a.

An example of the third gas may include an O- and H-containing gas. Examples of the O- and H-containing gas may include a H₂O gas, a H₂O₂ gas, and the like. Further, Examples of the O- and H-containing gas may include an O-containing gas and a H-containing gas such as an O₂ gas+H₂ gas. When these gases are used as the third gas, the surface of the base 200 a is terminated with a hydroxyl group (OH) in step C. That is, in this case, an OH termination is formed as an adsorption site on the surface of the base 200 a. When the OH termination is formed as the adsorption site on the surface of the base 200 a, a gas, such as the aforementioned aminosilane-based gas or the like, that reacts with the OH termination may be used as the first gas in some embodiments.

Further, an example of the third gas may include a N- and H-containing gas. Examples of the N- and H-containing gas may include a NH₃ gas, a N₂H₄ gas, a N₂H₂ gas, and the like. When these gases are used as the third gas, the surface of the base 200 a is terminated with a NH group in step C. That is, in this case, a NH termination is formed as an adsorption site on the surface of the base 200 a. When the NH termination is formed as the adsorption site on the surface of the base 200 a, a gas, such as the aforementioned halosilane-based gas or alkylhalosilane-based gas, that reacts with the NH termination may be used as the first gas in some embodiments. In this case, the aforementioned chlorosilane-based gas or alkylchlorosilane-based gas may be used as the halosilane-based gas or alkylhalosilane-based gas in some embodiments.

Further, as the third gas, for example, a N- and H-containing gas or a N-containing gas may be plasma-excited and used. For example, as the third gas, an NH₃ gas, a N₂H₄ gas, a N₂H₂ gas, a N₂ gas, and the like may be plasma-excited and used. When the N- and H-containing gas is plasma-excited and used as the third gas, a gas containing active species (for example, radicals) such as NH₃*, NH₂*, and NH* is supplied to the surface of the base 200 a. In this case, in step C, the surface of the base 200 a is terminated with a NH group, and a NH termination is formed as an adsorption site on the surface of the base 200 a. When the N-containing gas is plasma-excited and used as the third gas, a gas containing active species (for example, radicals) such as N₂* and N* is supplied to the surface of the base 200 a. In this case, in step C, the surface of the base 200 a is terminated with N, and a N termination is formed as an adsorption site on the surface of the base 200 a. When the NH termination is formed as the adsorption site on the surface of the base 200 a, a gas, such as the aforementioned halosilane-base gas or alkylhalosilane-based gas, that reacts with the NH termination may be used as the first gas in some embodiments. In this case, the aforementioned chlorosilane-based gas or alkylchlorosilane-based gas may be used as the halosilane-based gas or alkylhalosilane-based gas in some embodiments. When the N termination is formed as the adsorption site on the surface of the base 200 a, a gas, such as the aforementioned aminosilane-based gas, that reacts with the N termination may be used as the first gas.

According to these embodiments, the same effects as those in the aforementioned embodiments may be achieved. Further, according to these embodiments, the adsorption of the first gas on the surface of the base 200 a may be promoted, which makes it possible to shorten the processing time in step A. Further, in step A, the adsorption layer of the first gas may be more uniformly formed in the surface of the base 200 a, and further, a density of the adsorption layer of the first gas formed on the surface of the base 200 a may be increased, which makes it possible to generate the etching species more uniformly in the surface of the base 200 a in step B. This enables a further conformal etching process.

These embodiments are particularly effective when the modification reaction by adsorption is generated in step A.

Further, for example, as shown in FIG. 9A, the cycle including non-simultaneously performing step A and step B may be performed a predetermined number of times on the wafer 200 having a surface on which a base 200 e as a second film made of material different from that of the base 200 a, in addition to the base 200 a as a first film, is exposed. The base 200 a as the first film includes, for example, a silicon-based nitrogen-containing film such as a silicon nitride film (SiN film). Further, the base 200 e as the second film includes, for example, a silicon-based oxygen-containing film such as a silicon oxide film (SiO film).

These embodiments are different from the aforementioned embodiments in that the wafer 200 having the surface on which the base 200 a and the base 200 e are exposed is used, and the etching process in these embodiments may be performed in the same manner as the etching processes in the aforementioned embodiments. That is, a processing sequence and a processing condition of the etching process in these embodiments may be the same as those of the etching process in the aforementioned embodiments.

By performing the cycle a predetermined number of times, the cycle including non-simultaneously performing step A and step B, on the wafer 200 having a surface on which the base 200 a and the base 200 e are exposed, it is possible to selectively etch the base 200 a with respect to the base 200 e, as shown in FIGS. 9B and 9C. That is, by performing the cycle a predetermined number of times, the cycle including non-simultaneously performing step A and step B, on the wafer 200 having the surface on which the base 200 a and the base 200 e are exposed, it is possible to promote the etching of the base 200 a while suppressing the etching of the base 200 e. It is considered that this is because in the etching process in the aforementioned embodiments, the aforementioned various kinds of reactions are generated on the surface of the base 200 a while the aforementioned various kinds of reactions are unlikely to be generated on the surface of the base 200 e. FIG. 9B shows a state of the surface of the wafer 200 during the etching process, and FIG. 9C shows a state of the surface of the wafer 200 after the etching process is completed.

According to these embodiments, the base 200 a may be etched with respect to the base 200 e with a selectivity of 5:1 or more, a selectivity of 10:1 or more, or a selectivity of 20:1 or more. Further, according to these embodiments, the base 200 a may be etched with respect to the base 200 e with a selectivity of 30:1 or more, a selectivity of 40:1 or more, a selectivity of 50:1 or more, and furthermore with more selectivity. Further, according to these embodiments, depending on conditions, the base 200 a can be etched without substantially etching the base 200 e. In the present disclosure, “etching the base 200 a with respect to the base 200 e with a selectivity of 5:1 or more” means that the etching amount of the base 200 a is “5” or more when the etching amount of the base 200 e is “1.”

In this way, according to these embodiments, it is possible to promote the etching of the base 200 a while suppressing the etching of the base 200 e, which makes it possible to etch the base 200 a with respect to the base 200 e with high selectivity. That is, according to these embodiments, a so-called selective etching in which a specific film is selectively etched is possible. Further, according to these embodiments, it is possible to improve the controllability of the etching amount in the selective etching.

In these embodiments, the base 200 a may include a nitride film and the base 200 e may include a film (for example, an oxide film) other than the nitride film in some embodiments. In some embodiments, the base 200 a may include a silicon nitride film and the base 200 e may include a film (for example, a silicon oxide film) other than the silicon nitride film. Further, in some embodiments, the base 200 a may include a nitrogen-containing film and the base 200 e may include a film (for example, an oxygen-containing film) other than the nitrogen-containing film. Further, in some embodiments, the base 200 a may include a silicon- and nitrogen-containing film and the base 200 e may include a film (for example, a silicon- and oxygen-containing film) other than the silicon- and nitrogen-containing film. When the base 200 a and the base 200 e are in such a combination, the aforementioned effects may be particularly exhibited. However, the base 200 a may be a film other than the nitride film (silicon nitride film, nitrogen-containing film, and silicon- and nitrogen-containing film). Further, the base 200 e may be a film other than the oxide film (silicon oxide film, oxygen-containing film, and silicon- and oxygen-containing film).

For example, as in the aforementioned embodiments, the base 200 a as the first film may be at least one selected from the group of a SiN film, a SiCN film, a N-rich SiON film, a N-rich SiOCN film, a SiBN film, a SiBCN film, a BN film, a TiN film, a WN film, a W film, a Mo film, a Si film, a Ge film, and a SiGe film. Further, as in the aforementioned embodiments, the O-containing film such as the SiON film or the SiOCN film as the first film may be a N-rich film, that is, a film having a higher N concentration in the film than an O concentration in the film. In this way, the base 200 a as the first film may be a nitrogen-containing film such as a silicon-based nitride film (silicon-based nitrogen-containing film) such as a SiN film, a SiCN film, a N-rich SiON film, a N-rich SiOCN film, a SiBN film, or a SiBCN film, a boron-based nitride film (boron-based nitrogen-containing film) such as a BN film, or a metal-based nitride film (metal-based nitrogen-containing film) such as a TiN film or a WN film, a metal film (transition metal film or transition metal single film) such as a W film or a Mo film, or a semiconductor film such as a Si film, a Ge film, or a SiGe film.

The base 200 e as the second film may be at least one selected from the group of a silicon oxide film (SiO film), a silicon oxycarbide film (SiOC film), an oxygen-rich silicon oxynitride film (SiON film), an oxygen-rich silicon oxycarbonitride film (SiOCN film), a titanium oxide film (TIO film), a hafnium oxide film (HfO film), a zirconium oxide film (ZrO film), an aluminum oxide film (AlO film), and an aluminum film (Al film).

Further, in some embodiments, the O-containing film such as the SiON film or the SiOCN film as the second film may be an O-rich film, that is, a film having a higher O concentration in the film than a N concentration in the film. That is, in some embodiments, the SiON film and the SiOCN film may be an O-rich SiON film and an O-rich SiOCN film, respectively. Even in a case where the second film contains N in addition to O, when the O concentration is higher than the N concentration, it is possible to suppress the etching of the second film with the method of the aforementioned embodiments.

In this way, the base 200 e as the second film may be an oxygen-containing film such as a silicon-based oxide film (silicon-based oxygen-containing film) such as a SiO film, a SiOC film, an O-rich SiON film, or an O-rich SiOCN film, or a metal-based oxide film (metal-based oxygen-containing film) such as a TiO film, a HfO film, a ZrO film, or an AlO film, or a metal film (non-transition metal film or non-transition metal single film) such as an Al film.

Further, for example, a plurality of films such as a second film (the base 200 e) and a third film, in addition to the first film (the base 200 a), may be exposed on the surface of the wafer 200. The films (specifically, the first film, the second film, the third film, and the like) exposed on the surface of the wafer 200 may be the film exemplified as the first film or the film exemplified as the second film.

For example, a SiN film, a SiO film, and a Si film may be exposed as the first film, the second film, and the third film, respectively, on the surface of the wafer 200. In this case, the SiN film and the Si film may be selectively etched with respect to the SiO film. Further, for example, a SiCN film, a SiOC film, and an AlO film may be exposed as the first film, the second film, and the third film, respectively, on the surface of the wafer 200. In this case, the SiCN film may be selectively etched with respect to the SiOC film and the AlO film. Further, for example, a N-rich SiOCN film, an O-rich SiOCN film, a N-rich SiON film, and an O-rich SiON film may be exposed as the first film, the second film, the third film, and a fourth film, respectively, on the surface of the wafer 200. In this case, it is possible to selectively etch the N-rich SiOCN film and the N-rich SiON film with respect to the O-rich SiOCN film and the O-rich SiON film. In these cases, the same effects as those in the aforementioned embodiments may be achieved.

Recipes used in each process may be provided individually according to the processing contents and may be stored in the memory device 121 c via a telecommunication line or the external memory device 123. Moreover, at the beginning of each process, the CPU 121 a may properly select an appropriate recipe from a plurality of recipes stored in the memory device 121 c according to the processing contents. Thus, it is possible for a single substrate processing apparatus to realize various types of etching processes with enhanced reproducibility. Further, it is possible to reduce an operator's burden and to quickly start each process while avoiding an operation error.

The aforementioned recipes are not limited to newly-provided ones but may be provided, for example, by modifying the existing recipes that are already installed in the substrate processing apparatus. When the recipes are modified, the modified recipes may be installed in the substrate processing apparatus via a telecommunication line or a recording medium storing the recipes. In addition, the existing recipes already installed in the substrate processing apparatus may be directly modified by operating the input/output device 122 of the substrate processing apparatus.

In the aforementioned embodiments, there have been described examples in which an etching process is performed by using a batch-type substrate processing apparatus capable of processing a plurality of substrates at a time. The present disclosure is not limited to the aforementioned embodiments, but may be suitably applied, for example, to a case where an etching process is performed by using a single-wafer-type substrate processing apparatus capable of processing a single substrate or several substrates at a time. Further, in the aforementioned embodiments, there has been described examples in which an etching process is performed by using a substrate processing apparatus including a hot-wall-type process furnace. The present disclosure is not limited to the aforementioned embodiments, but may be appropriately applied to a case where an etching process is performed by using a substrate processing apparatus including a cold-wall-type process furnace.

Even in the case of using these substrate processing apparatuses, each process may be performed with processing sequences and processing conditions similar to those of the aforementioned embodiments to achieve effects similar to those of the aforementioned embodiments.

The aforementioned embodiments may be appropriately combined with one another. The processing sequences and process conditions used in this case may be similar to, for example, the processing sequences and process conditions of the aforementioned embodiments.

EXAMPLES Comparative Example 1

Bu using the aforementioned substrate processing apparatus, the first gas is used alone to perform an etching process on a SiN film and a SiO film exposed on a surface of a wafer, and etching amounts of the films are measured. As the first gas, one selected from the group of the fluorine-based gases exemplified as the first gas in the aforementioned embodiments is used. A process condition is set to a predetermined condition within a range of the process condition in the aforementioned step A, except that a processing temperature is set to 100 degrees C., 250 degrees C., 350 degrees C., or 400 degrees C.

FIG. 6 shows a measurement result of the etching amount in Comparative Example 1. The horizontal axis in FIG. 6 represents the processing temperature (degrees C.), and the vertical axis in FIG. 6 represents the etching amounts (Å) of the SiN film and the SiO film respectively. Further, in FIG. 6 , a mark ▪ indicates the measurement result of the etching amount of the SiO film, and a mark ● indicates the measurement result of the etching amount of the SiN film.

From FIG. 6 , it can be seen that in the case of a process with the first gas alone, none of the SiN film and the SiO film are etched when the processing temperature is 100 to 250 degrees C. On the other hand, when the processing temperature exceeds 250 degrees C., it can be seen that even when the process is performed with the first gas alone, the SiN film is etched and the SiO film is slightly etched.

Comparative Example 2

By using the aforementioned substrate processing apparatus, the second gas is used alone to perform an etching process on a SiN film and a SiO film exposed on the surface of a wafer, and etching amounts of the films are measured. As the second gas, a gas having a molecular structure different from that of the first gas in Comparative Example 1, which is one selected from the group of the fluorine-based gases exemplified as the second gas in the aforementioned embodiments, was used. A process condition is set to a predetermined condition within a range of the process condition in the aforementioned step B, except that the processing temperature is set to 35 degrees C. or 100 degrees C.

FIG. 7 shows the measurement result of the etching amount in Comparative Example 2. The horizontal axis in FIG. 7 represents the processing temperature (degrees C.), and the vertical axis in FIG. 7 represents the etching amount (Å) of the SiN film and the SiO film respectively. Further, in FIG. 7 , a mark ▪ indicates the measurement result of the etching amount of the SiO film, and a mark ● indicates the measurement result of the etching amount of the SiN film.

From FIG. 7 , it can be seen that in the case of a process with the second gas alone, none of the SiN film and the SiO film are etched when the processing temperature is 35 to 100 degrees C. Further, in the case of the process with the second gas alone, it is confirmed that when the processing temperature is 100 to 250 degrees C., there is a tendency that none of the SiN film and the SiO film are etched. Further, even in the case of the process with the second gas alone, it is confirmed that when the processing temperature exceeds 250 degrees C., there is a tendency that both the SiN film and the SiO film are slightly etched. Further, even in the case of the process with the second gas alone, it is confirmed that when the processing temperature is 400 degrees C. or higher, there is a tendency that both the SiN film and the SiO film are etched.

EXAMPLES

Using the aforementioned substrate processing apparatus, according to the processing sequence shown in FIG. 4 , an etching process is performed on a SiN film and a SiO film exposed on the surface of a wafer, and etching amounts of the films are measured. As the first gas, the same gas as the first gas in Comparative Example 1 is used, and as the second gas, the same gas as the second gas in Comparative Example 2 is used. The process condition is set to a predetermined condition within a range of the process conditions in the aforementioned step A and step B, except that the processing temperature is set to 100 degrees C.

FIG. 8 shows the measurement result of the etching amount in Example. For comparison, the etching amounts when the processing temperatures in Comparative Example 1 and Comparative Example 2 are 100 degrees C. are also shown in FIG. 8 . The vertical axis in FIG. 8 represents the etching amounts (Å) of the SiN film and the SiO film. In FIG. 8 , a mark ▪ indicates the measurement result of the SiO film, and a mark ● indicates the measurement result the SiN film.

As shown in FIG. 8 , at the processing temperature of 100 degrees C., even in the case of a process with the first gas alone (Comparative Example 1) and even in the case of a process with the second gas alone (Comparative Example 2), it can be seen that none of the SiN film and the SiO film are etched. On the other hand, in Example, by performing the etching process according to the processing sequence shown in FIG. 4 at the processing temperature of 100 degrees C., it can be seen that the SiO film is hardly etched, but the etching amount of the SiN film is close to 80Å. Further, in Example shown in FIG. 8 , it can be seen that the SiN film can be etched with respect to the SiO film with a selectivity of 35:1 to 45:1.

Such a difference in the etching amount, that is, a difference between the etching amount of the SiO film in Comparative Example 1, Comparative Example 2, and Example and the etching amount of the SiN film in Example, has a similar tendency at least within a range of the processing temperature of 25 to 250 degrees C. Further, such a difference in the etching amount has a similar tendency even within a range of 250 to 400 degrees C. Therefore, when the etching process is performed according to the processing sequence shown in FIG. 4 , the processing temperature may be specifically in the range of 25 to 400 degrees C., or more specifically in the range of 25 to 250 degrees C.

According to the present disclosure in some embodiments, it is possible to provide a technique of enhancing a controllability of an etching amount.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the embodiments described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures. 

What is claimed is:
 1. A method of processing a substrate, comprising: etching a first base on a surface of a substrate by alternately performing: (a) forming a first layer on at least a portion of a surface of the first base by supplying a first gas to the substrate; and (b) forming an etching species by supplying a second gas having a molecular structure different from that of the first gas to the substrate to perform at least one selected from the group of causing the second gas to react with the first layer and activating the first layer with the second gas, wherein in (b), a second layer, which is removable by the first gas, is formed on at least a portion of a surface of the first base after being subjected to contact with the etching species.
 2. The method of claim 1, wherein in (a), the first layer is formed by causing at least a portion of molecules of the first gas to be physically adsorbed or chemically adsorbed on the at least a portion of the surface of the first base.
 3. The method of claim 1, wherein in (a), the first layer is formed by generating a compound by a chemical reaction between at least a portion of molecules of the first gas and atoms or molecules of the at least a portion of the surface of the first base.
 4. The method of claim 1, wherein in (b), the second gas is supplied to the substrate under a condition that the reaction between the second gas and the first layer is more predominant than a reaction between the second gas and the first base.
 5. The method of claim 1, wherein in (b), the second gas is supplied to the substrate under a condition that the reaction between the second gas and the first layer progresses and a reaction between the second gas and the first base does not progress.
 6. The method of claim 1, wherein in (b), the second gas is supplied to the substrate under a condition that the activation of the first layer with the second gas is more predominant than an activation of the first base with the second gas.
 7. The method of claim 1, wherein in (b), the second gas is supplied to the substrate under a condition that the activation of the first layer with the second gas progresses and an activation of the first base with the second gas does not progress.
 8. The method of claim 1, wherein in (b), the second gas is supplied to the substrate under a condition that a reaction between the etching species and the at least a portion of the first base is more predominant than a reaction between the second gas and the first base.
 9. The method of claim 1, wherein in (b), the second gas is supplied to the substrate under a condition that a reaction between the etching species and the at least a portion of the first base progresses and a reaction between the second gas and the first base does not progress.
 10. The method of claim 1, wherein in (b), the at least a portion of the surface of the first base is removed with the etching species and the second layer is formed on at least a portion of a surface of the first base from which at least the portion is removed.
 11. The method of claim 1, wherein a cycle including (a) and (b) is performed two or more times in the etching, wherein the cycle includes a first cycle and at least one subsequent cycle, and wherein in (a), in the at least one subsequent cycle, the second layer is removed by causing the first gas to react with the second layer by supplying the first gas to the substrate, and the first layer is formed on at least a portion of a surface of the first base from which the second layer is removed.
 12. The method of claim 1, wherein the first base includes a nitrogen-containing film, a transition metal film, or a semiconductor film.
 13. The method of claim 1, wherein the surface of the substrate further includes a second base, and wherein the first base is selectively etched with respect to the second base in the etching.
 14. The method of claim 13, wherein the first base includes a nitrogen-containing film, a transition metal film, or a semiconductor film, and the second base includes an oxygen-containing film or a non-transition metal film.
 15. The method of claim 14, wherein the nitrogen-containing film includes a silicon-based nitrogen-containing film, a boron-based nitrogen-containing film, or a metal-based nitrogen-containing film.
 16. The method of claim 14, wherein the oxygen-containing film includes a silicon-based oxygen-containing film or a metal-based oxygen-containing film.
 17. The method of claim 13, wherein the first base is etched with respect to the second base with a selectivity of 5:1 or more in the etching.
 18. The method of claim 1, wherein the first gas includes one or more selected from the group of a silicon-containing gas, a metal-containing gas, an oxygen-containing gas, a nitrogen- and hydrogen-containing gas, a boron-containing gas, a phosphorus-containing gas, and a halogen-containing gas, and wherein the second gas includes one or more selected from the group of the halogen-containing gas and an acetylacetone-based gas.
 19. The method of claim 1, wherein the etching is performed under a non-plasma atmosphere.
 20. The method of claim 1, wherein the etching is performed under a condition that an etching reaction of the first base is difficult to continue when at least one selected from the group of the first gas and the second gas is present alone.
 21. A method of manufacturing a semiconductor device, comprising: etching a first base on a surface of a substrate by alternately performing: (a) forming a first layer on at least a portion of a surface of the first base by supplying a first gas to the substrate; and (b) forming an etching species by supplying a second gas having a molecular structure different from that of the first gas to the substrate to perform at least one selected from the group of causing the second gas to react with the first layer and activating the first layer with the second gas, wherein in (b), a second layer, which is removable by the first gas, is formed on at least a portion of a surface of the first base after being subjected to contact with the etching species.
 22. A non-transitory computer-readable recording medium storing a program that causes, by a computer, a substrate processing apparatus to perform a process comprising: etching a first base on a surface of a substrate by alternately performing: (a) forming a first layer on at least a portion of a surface of the first base by supplying a first gas to the substrate; and (b) forming an etching species by supplying a second gas having a molecular structure different from that of the first gas to the substrate to perform at least one selected from the group of causing the second gas to react with the first layer and activating the first layer with the second gas, wherein in (b), a second layer, which is removable by the first gas, is formed on at least a portion of a surface of the first base after being subjected to contact with the etching species.
 23. A substrate processing apparatus configured to perform the method of claim
 1. 